Soap stabilization



SOAP STABILIZATION John G. Kleyn, Creve Coeur, Mo., assignor to MonsantoChemical Company, St. Louis, Mo., a corporation of Delaware No Drawing.Application January 7, 1955 Serial No. 480,619

9 Claims. (Cl. 252-107) The present invention relates to the lightstability of soap and particularly to means of improving the light andcolor stability of soaps during storage and use conditions. Practicallyall soaps, even when wrapped in paper or enclosed in a box tend todiscolor under normal storage conditions probably due to penetration bythe shorter wave lengths of light and this tendency is most marked inthe case of white soaps, which frequently, after shelf storage for aperiod of time, change to cream, to tan or at times to a light browncolor particularly at the ends of the cake of soap and even all over thesurface thereof.

The darkening or discoloration of soaps is frequently found among thehigher priced toilet soaps many of which also contain small quantitiesof a phenolic compound which is used as an antiseptic or preventive ofrancidity. While the discoloration of a soap does not adversely affectits utilitarian properties, it is none the less very objectionable froman esthetic viewpoint, and lowers the sales appeal of the product.

Many attempts have been directed to overcome the storage discolorationof soap. These have met with varying degrees of success but the problemhas been intensified by the practice of incorporating phenolic compoundsinto soap. Unfortunately the materials known for stabilizing soap havenot proved effective in the presence of a phenolic compound. However, ithas now been found possible greatly to enhance the light stability ofsoap containing a phenolic compound by incorporating therein an ultraviolet light absorber and agdygjng, agent, preferably an i ri oggr 1i cs lfite possessing mild ,reducing properties. Effec ive reducing agentsfor the objects desired compris sodium bisulfite and sodiumhydrosulfite. e various ingredients required for practicing the presentinvention may be compounded into a soap by any of the methods well known3 in the art.

One such method is to prepare test bars of soap by simulating theamalgamator stage in soap manufacture, that is, the stage whereinperfumes and other additives if required, are introduced and blended inthe soap base. As a soap base in the following experiments, white highgrade soap chips of a type commonly employed for toilet use or forwashing delicate fabrics and containing approximately 6% water wasemployed. A portion of the base soap chips was blended in a WaringBlendor with 2% by weight of a phenolic antiseptic, for example 2,2-thiobis(4,6-dichlorphenol) and also an ultra violet light absorber. Theabsorber employed in different experiments was 2% and of2-hydroxy-4-methoxy-benzophenone on the weight of the phenolicantiseptic or in other words 0.04% and 0.10% respectively of the weightof the base soap chips. Sodium sulfite in different experiments wasadded in quantities equal respectively to 5%, 12.5%, 25% and 100% byweight of the phenolic antiseptic. These quantities of sulfitecorrespond respectively to 0.10%, 0.25%, 0.50% and 2% of Patented Jan.19, 1960 ICC the weight of the base soap chips where 2% by weight of thephenolic antiseptic was employed. The soap composition was blended in amortar with sufiicient water to bring the moisture content to 10% byweight. Test bars of the compounded soaps were then pressed from themoist mix by means of a suitable die operated by bench vise pressure.However, in the case of these experiments where concentrations of sodiumsulfite in amount equal to and greater than 25% of the weight of thephenolic antiseptic were taken, it was preferred to add the sulfite asan approximately 13% water solution, then to add additional water to themass to form approximately a soap slurry and then to dry on a steamtable of not more than 50 pounds per square inch gauge pressure.Thereupon the dried material was reblended, brought back to 10% watercontent and pressed into bars by the method previously mentioned. Thelight reflectance of these various test soap bars was then taken beforeand after exposure 15 minutes under a General Electric Type RS Sun Lamp7 inches from the soap. During this period of exposure the test barswere maintained as nearly as possible at a temperature of 70 C. by meansof air cooling.

In all cases it was noted that while increasing quantities of reducingagent up to 25% of the weight of the phenolic antiseptic showed lesserdifferences in the refiectance of unexposed and light exposed soap,further increases above 25% of the reducing agent failed to show anygreatly marked improvement. The same phenomena was shown in the case ofpercent increase in light stability, the reference standard beingpure'soap. Thus, a increase in stability is that which would bring thesoap containing the phenolic antiseptic to the stability of pure soap.With a 12.5% dosage of sodium sulfite on the weight of the phenolicantiseptic but with no ultra violet light absorber, there was a 21%increase in stability, with 25% of sodium sulfite there was a 33%increase in light stability and the same increase with 100% sulfite. Inanother test portion containing 2% of the ultra violet light absorber onthe weight of phenolic antiseptic, using 12.5% of the reducing agent inthe manner described, there was noted a 27% increase in light stability,with 25% sulfite there was a 43% improvement while with a 100% dosage ofsulfite there was a 49% improvement in light stability. In anotherseries of tests containing 5% of the ultra violet light absorber on theweight of phenolic antiseptic, and using 12.5% of the sodium sulfite inthe manner described, there was observed a 33% increase in lightstability, with 25 sulfite there was a 59% improvement, while with a100% dosage of sulfite there was an improvement of 62% in lightstability. It is apparent that the addition of a mild reducing agent,specifically sodium sulfite, to the ultra violet light absorber has verymaterially improved the light stability of a white soap containing aphenolic antiseptic.

There was even less change in color after exposure to ultra violet lightwhen the absorber was co-precipitated with the phenolic antiseptic andthe composite mixture used to compound bar soap. Approximately 30 partsby weight of 2,2-thiobis(4,6-dichlorphenol) (0.0842 molecularproportions) and 1.5 parts by weight of 2-hydroxy-4-methoxy-benzophenone (0.0066 molecular proportions) weredissolved in about 25 parts of acetone and sodium hydroxide addedsufficient to form the monosodium salt of each ingredient. The mixturewas diluted with water and the phenolic ingredients precipitated fromsolution by adding 10% sulfuric acid (0.102 gram moles per 100 grams).The solids were removed by filtration, washed and dried. The compositemixture was used to compound bar soap from high grade white soap chipsas hereinbefore described. The amount added was 2% of the weight of thesoap. Also, 0.25% sodium bisulfite was added. After exposure to ultraviolet light the color was almost indistinguishable from that of a barof pure soap similarly exposed.

Similar improvements were observed in soap solu- 5 tions. Tests wereconducted by preparing solutions containing 5% soap (a mixture of 80%sodium soap and potassium soap produced from a 70% tallow and 30%coconut oil glyceride), 0.1% of the phenolic antiseptic together withthe stabilizer, and observing the 10 color of the solutions afterstanding. The table summarizes typical results after 12 days in a sunnyroom.

The evidence indicates that the ultra violet light absorber selectedshould absorb strongly in the range of wave length absorbed by thephenolic antiseptic. For example, the absorption by2,2-thiobis(4,6-dichlorphenol) reaches a maximum at 320-340 mu and isquite strong over the entire range of 300-350 mu and the most effectivescreening agents exhibited strong absorption in the 300-350 mu range.The absorption by 2- hydroxy-4-methoxy-benzophenone reaches a maximum inthis range. Still other suitable ultra violet light absorbers are2-hydroxy-4,4-dimethoxy-benzophenone, isobutyl paminobenzoate, n-butylp-aminobenzoate. Many others are available under proprietary names.

Discoloration of soaps containing phenolic antiseptics is a generalphenomenon and through application of the principles of this inventionvaluable properties imparted to soap by phenolic antiseptics can besecured without objectionable discoloration. Other phenolic antisepticsinclude 2,2'-thiobis-p-cresol, 2,2-thiobis (p-chlorophenol),2,2'-methylenebis(p-chlorophenol) and 2,2-methylenebis(3,4,6-trichlorphenol).

It is intended to cover all changes and modifications of the examples ofthe invention herein chosen for purposes of disclosure which do notconstitute departures from the spirit and scope of the invention.

What is claimed is:

1. The method of improving the light stability of an antisepticdetergent composition comprising a detgrgen];

containing a minor proportion of a phenolic antiseptic effective in thepresence of soap and selected from the group consisting ofthiobis(chloro phenol) antiseptics, methylene-bis(chloro phenol)antiseptics and 2,2'-thiobis p-cresol, which antiseptic discolors thesoap when the composition is exposed to light which comprisesincorporating therein a small amount sufficient to increase the lightstability, of a mild reducing agent selected from the group consistingof sodium sulfite, s ggg m bisulfite and sodium hydrosulfite togetherwith a small amount sulficient further to increase the light stabilityof an ultra violet absorber selected from the group consisting of 2-hydroxy 4-methoxy benzophenone, Z-hydroxy 4,4'-dimethoxy benzophenone,isobutyl p-amino benzoate and n-butyl p-amino benzoate.

2. The method of improving the light stability of an antisepticdetergent composition comprising a detergent soap containing a minorproportion of a thiobis-(chlorophenol) antiseptic which discolors thesoap when the composition is exposed to light which comprisesincorporating therein a small amount sufficient to increase the lightstability of sodium sulfite together with a small amount sufiicientfurther to increase the light stability of an ultra violet lightabsorber selected from the group consisting of 2-hydroxy-4-methoxybenzophenone, 2 bydroxy 4,4-dimethoxy benzophenone, isobutylp-aminobenzoate and n-butyl p-aminobenzoate.

3. The method of improving the light stability of an antisepticdetergent composition comprising a detergent soap containing a minorproportion of 2,2-thiobis(4,6- dichlorophenol) which composition ischaracterized by discoloration upon exposure to light which comprisesincorporating therein a small amount sufiicient to increase the lightstability of sodium sulfite together with a small amount sufiicientfurther to increase the light stability of 2-hydroxy-4-methoxybenzophenone.

4. In the method of claim 3 the step which comprises coprecipitatingfrom aqueous alkaline solution the 2,2- thiobis(4,6-dichlorophenol) andthe 2-hydroxy-4-methoxy benzophenone and incorporating the compositemixture into the soap.

5. An antiseptic detergent composition comprising a detergent soapcontaining a minor proportion of a phenolic antiseptic selected from thegroup consisting of thiobis(chloro phenol) antiseptics, methylenebis(chloro phenol) antiseptics and 2,2'-thiobis p-cresol effective inthe presence of soap which discolors the soap when the composition isexposed to light stabilized by having incorporated therein a smallamount sufiicient to increase the light stability, of a mild reducingagent selected from the group consisting of sodium sulfite, sodiumbisulfite and sodium hydrosulfite together with a small amountsufficient further to increase the light stability, of an ultra violetabsorber selected from the group consisting of 2-hydroxy 4-methoxybenzophenone, 2-hydroxy 4,4- dimethoxy benzophenone, isobutyl p-aminobenzoate and n-butyl p-amino benzoate.

6. An antiseptic detergent composition comprising a detergent soapcontaining a minor proportion of a thiobis (chloro phenol) antisepticwhich discolors the soap when the composition is exposed to lightstabilized by having incorporated therein a small amount sufiicient toincrease the light stability of sodium sulfite together with a smallamount sufficient further to increase the light stability of an ultraviolet light absorber selected from the group consisting of2-hydroxy-4-methoxy benzophenone, 2-hydroxy 4,4-dimethoxy benzophenone,isobutyl p-aminobenzoate and n-butyl p-aminobenzoate.

7. An antiseptic detergent composition comprising a detergent soapcontaining a minor proportion of 2,2- thiobis(4,6-dichlorophenol) whichcomposition is characterized by discoloration upon exposure to lightstabilized by having incorporated therein a small amount sufficient toincrease the light stability of sodium sulfite together with a smallamount sufficient further to increase the light stability of2-hydroxy-4,4'-dimethoxy benzophenone.

8. An antiseptic detergent composition comprising a detergent soapcontaining a minor proportion of the antiseptic2,2'-thiobis-(4,6-dichlorophenol) which composition is characterized byhaving incorporated therein sodium sulfite within the range of 12.5%-500% by weight of the said antiseptic sufficient to increase the lightstability together with 2-hydroxy-4-methoxy benzophenone within therange of 2%-50% by weight of the antiseptic sutficient further toincrease the light stability.

9. An antiseptic detergent composition comprising a detergent soapcontaining a minor proportion of 2,2- thiobis-(4,6-dichlorophenol) whichcomposition is characterized by discoloration upon exposure to lightstabilized by having incorporated therein a small amount sufiicient toincrease the light stability of sodium bisulfite together with a smallamount sufficient further to increase the light stability of an ultraviolet light absorber selected from the group consisting of 2-hydroxy4-methoxy benzophenone, 2-hydroxy 4,4-dimethoxy benzophenone,isobutyl-p-amino benzoate and n-butyl-p amino benzoate.

(References on following page) References Cited in the file of thispatent UNITED STATES PATENTS Reed Feb. 4, 1936 Kunz et a1. Dec. 26, 1950Mackey Sept. 25, 1951 Chiddix et a1 July 20, 1954 Hoch Nov. 2, 1954 Bellet al Aug. 21, 1956 FOREIGN PATENTS Great Britain May 2, 1918 OTHERREFERENCES 6 et al., January 1953, pp. 34-37, 90.

Soap and Sanitary Chemicals, December 1941, article by Fiore, pp. 30-33,75, 77.

1. THE METHOD OF IMPROVING THE LIGHT STABILITY OF AN ANTISEPTICDETERGENT COMPOSITION COMPRISING A DETERGENT SOAP CONTAINING A MINORPROPORTION OF A PHENOLIC ANTISEPTIC EFFECTIVE IN THE PRESENCE OF SOAPAND SELECTED FROM THE GROUP CONSISTING OF THIOBIS(CHLORO PHENOL)ANTISEPTICS, METHYLENE-BIS(CHLO PHENOL) ANTISEPTICS AND 2,2''-THIOBISP-CRESOL, WHICH ANTISEPTIC DISCOLORS THE SOAP WHEN THE COMPOSITION ISEXPOSED TO LIGHT WHICH COMPRISES INCORPORATING THEREIN A SMALL AMOUNTSUFFICIENT TO INCREASE THE LIGHT STABILITY, OF A MILD REDUCING AGENTSELECTED FROM THE GROUP CONSISTING OF SODIUM SULFITE, SODIUM BISULFITEAND SODIUM HYDROSULFITE TOGETHER WITH A SMALL AMOUNT SUFFICIENT FURTHERTO INCREASE THE LIGHT STABILITY OF AN ULTRA VIOLET ABSORBER SELECGEDFROM THE GROUP CONSISTING OF 2HYDROXY 4-METHOXY BENZOPHENONE, 2-HYDROXY4,4''-DIMETHOXY BENZOPHENONE, ISOBUTYL P-AMION BENZOATE ANDN-BUTYL-P-AMION BENZOATE.